Verizon Communications had earlier filed in support of the challenge, stating that its cloud business could be affected

AT&T is backing Microsoft in its challenge of a U.S. search warrant for private email communications located in a facility in Dublin, Ireland.

The telecommunications company on Thursday filed in a New York court asking permission to submit an amicus curiae brief in support of Microsoft. Described as a "friend of the court," an amicus curiae is not directly involved in a litigation but believes it may be impacted or has views on the matter before the court.

Verizon Communications also filed this week in opposition of the warrant in a dispute that is regarded as having far-reaching implications on the ability of U.S. tech companies to win the trust of customers abroad for their services including cloud computing.

Microsoft has objected to the warrant issued by a magistrate judge under the Electronic Communications Privacy Act, as it purports to authorize the U.S. government to search Microsoft's facilities worldwide.

In April, U.S. Magistrate Judge James C. Francis IV refused to amend the warrant, holding that if territorial restrictions on conventional warrants were applied to warrants issued under section 2703 (a) of the Stored Communications Act (SCA), a statute that covers required disclosure of wire or electronic communications in electronic storage, law enforcement efforts would be seriously affected.

The companies have expressed concern that the U.S. government's demands for data held abroad could alienate overseas customers from placing their data with U.S. providers, particularly after the disclosures of surveillance abroad by the U.S. National Security Agency.

"Foreign customers will respond by moving their business to foreign companies without a presence in the United States," Verizon said in its filing.

A decision like the one by the magistrate judge could feed into concerns of customers abroad as it would appear that under SCA, U.S.-based providers alone may be compelled to give U.S. authorities access to information held anywhere in the world, without considering foreign law or whether the customer-provider relationship has any substantial nexus to the U.S., AT&T wrote in its proposed amicus brief in the U.S. District Court for the Southern District of New York.

AT&T said it works with the U.S. Federal Bureau of Investigation, under the Mutual Legal Assistance Treaty process, when it receives requests for information stored in the U.S. from law enforcement agencies abroad, to ensure that any resulting data transfer occurs pursuant to a warrant or other form of process specified by the SCA, and is otherwise consistent with U.S. law. MLAT governs exchange of information between countries for law enforcement purposes.

"This practice rests on an understanding that when it comes to data storage and privacy protections, location matters," AT&T wrote in the filing, while stating that the SCA does not authorize U.S. courts to issue warrants requiring providers to disclose information stored in a foreign country without a substantial nexus to the U.S.

By the magistrate's approach, the law of the foreign place where the data is stored is irrelevant to whether the provider must disclose information to U.S. authorities, according to the filing. "If courts in this country adopt that approach, it seems safe to predict that foreign officials will likewise seek to forgo the MLAT process and demand that U.S. providers allow access to U.S.- based servers when presented with orders that satisfy foreign law," it added.

John Ribeiro covers outsourcing and general technology breaking news from India for The IDG News Service. Follow John on Twitter at @Johnribeiro. John's e-mail address is john_ribeiro@idg.com

This story, "AT&T Backs Microsoft's Dispute Over Warrant for Emails Held Abroad" was originally published by
IDG News Service Bangalore Bureau.